The present invention relates to polynucleotides and polypeptides involved in plant-fiber development and methods of using same.
The present invention relates to a novel computational approach that utilizes comparative genomics to identify genes which play a role in fiber development.
Cotton and cotton by-products provide raw materials that are used to produce a wealth of consumer-based products in addition to textiles including cotton foodstuffs, livestock feed, fertilizer and paper. The production, marketing, consumption and trade of cotton-based products generate an excess of $100 billion annually in the U.S. alone, making cotton the number one value-added crop.
It is estimated that the use of cotton as a fiber by humans dates back 7000 years in Central America and 5000 years in India. Even with the growth of synthetic fibers in the last 50 years, cotton still accounts for approximately 50% of the world's textile fiber [Agrow Reports, Global Seed markets DS208, October 2000].
Even though 90% of cotton's value as a crop resides in the fiber (lint), yield and fiber quality has declined, especially over the last decade [Meredith (2000), Proc. World Cotton Research Conference II, Athens, Greece pp. 97-101]. This decline has been attributed to general erosion in genetic diversity of cotton varieties, and an increased vulnerability of the crop to environmental conditions [Bowman et al., Crop Sci. 36:577-581 (1996); Meredith, supra].
There are many varieties of cotton plant, from which cotton fibers with a range of characteristics can be obtained and used for various applications. Cotton fibers may be characterized according to a variety of properties, some of which are considered highly desirable within the textile industry for the production of increasingly high quality products and optimal exploitation of modern spinning technologies. Commercially desirable properties include length, length uniformity, fineness, maturity ratio, decreased fuzz fiber production, micronaire, bundle strength, and single fiber strength. Much effort has been put into the improvement of the characteristics of cotton fibers mainly focusing on fiber length and fiber fineness. In particular, there is a great demand for cotton fibers of specific lengths.
Methods for improving the characteristics or yield of cotton fibers can be classified into the following three categories:
1. Variety Improvement by Cross Breeding
This method has been utilized most widely so far. At present, almost all the cultivated varieties of cotton plant are bred by this method. However, improvement of cotton fiber yield using traditional breeding is relatively slow and inefficient and the degree of variability which can be achieved is limited.
2. Treatment with Plant Hormones
Plant hormones such as auxin, gibberellin, cytokinin and ethylene have been widely used in field crops or horticultural products. The influence of plant hormones, particularly gibberellin, auxin and brassinolide, on the fiber characteristics of cotton plants is known [e.g. U.S. Pat. No. 5,880,110 produces cotton fibers with improved fiber characteristics by treatment with brassinosteroids]. However, no measurable effect has been documented, making practical use of these hormones on a large scale highly unlikely.
3. Variety Improvement by Genetic Engineering:
The broad acceptance of genetically engineered cotton in the leading producing countries and the fact that it is a non-food crop make it an attractive candidate for genetic engineering for improvement of fiber yield and/or quality.
In recent years, remarkable progress has been made in plant genetic engineering, as a result several cases of successful variety improvement of commercially important crop plants have been reported (e.g., cotton, soybean, corn, canola, tomato). For example, methods of improving insect resistance by the introduction of a gene coding for BT toxin (i.e., insecticidal protein toxin produced by Bacillus thuringiensis) in a cotton plant, have been developed and put to practical use. In addition, cotton plants with improved herbicide (Glyphosate) resistance have been genetically engineered by the introduction of a gene coding for 5-enol-pyruvil-shikimic acid 3-phosphate synthetase.
The availability and success of plant genetic engineering combined with the fact that cotton is an excellent candidate for genetic manipulation via recombinant techniques have led researchers to postulate that if a gene associated with an improved cotton fiber property could be identified, it could be up-regulated using recombinant techniques thus improving the characteristics or yield of cotton fibers. Conversely, if a gene associated with a decline in a cotton fiber property could be identified, it could be down-regulated using gene silencing methods. For this purpose, the mechanisms of fiber elongation and formation must be elucidated on the genetic level and genes closely associated with these mechanisms must be identified.
A cotton fiber is composed of a single cell that has differentiated from an epidermal cell of the seed coat, developing through four stages, i.e., initiation, elongation, secondary cell wall thickening and maturation stages. More specifically, the elongation of a cotton fiber commences in the epidermal cell of the ovule immediately following flowering, after which the cotton fiber rapidly elongates for approximately 21 days. Fiber elongation is then terminated, and a secondary cell wall is formed and grown through maturation to become a mature cotton fiber.
Several candidate genes have been isolated which are associated with the elongation and formation of cotton fibers. For example, five genes from cotton plants have been identified that are specifically expressed at the cotton fiber elongation stage by differential screening method and differential display method, [U.S. Pat. No. 5,880,100 and U.S. patent applications Ser. Nos. 08/580,545, 08/867,484 and 09/262,653].
WO0245485 describes methods and means to modulate fiber quality in fiber-producing plants, such as cotton, by modulating sucrose synthase (a sugar important for cell wall synthesis) activity and/or expression in such plants.
U.S. Pat. No. 6,472,588 and WO0117333 provide methods for increasing the quality of cotton fiber produced from a cotton plant by transformation with a DNA encoding sucrose phosphate synthase. The fiber qualities include strength, length, fiber maturity ratio, immature fiber content, fiber uniformity and micronaire.
WO9508914 discloses a fiber producing plant comprising in its genome a heterologous genetic construct. The genetic construct comprises a fiber-specific promoter and a coding sequence encoding a plant peroxidase, such as a cotton peroxidase.
WO9626639 provides methods whereby an ovary specific promoter sequence is utilized to express plant growth modifying hormones in cotton ovule tissue. The methods permit the modification of the characteristics of boll set in cotton plants and provide a mechanism for altering fiber quality characteristics such as fiber dimension and strength.
U.S. Pat. Nos. 5,981,834, 5,597,718, 5,620,882, 5,521,708 and 5,495,070 all disclose a method for genetically engineering a fiber-producing plant and the identification of cDNA clones useful for identifying fiber genes in cotton. The cDNA clones are useful in developing corresponding genomic clones from fiber producing plants to enable genetic engineering of cotton and other plants using these genes. Coding sequences from these isolated genes are used in sense or antisense orientation to alter the fiber characteristics of transgenic fiber producing plants.
U.S. patent applications U.S. 2002049999 and U.S. 2003074697 both disclose cotton plants of the genus Gossypium with improved cotton fiber characteristics. The cotton plant has an expression cassette containing a gene coding for an enzyme selected from the group consisting of endoxyloglucan transferase, catalase and peroxidase so that the gene is expressed in cotton fiber cells to improve the cotton fiber characteristics.
WO 01/40250 provides methods for improving cotton fiber quality by modulating transcription factor gene expression.
WO 96/40924 provides novel DNA constructs which may be used as molecular probes or alternatively inserted into a plant host to provide for modification of transcription of a DNA sequence of interest during various stages of cotton fiber development. The DNA constructs comprise a cotton fiber transcriptional initiation regulatory region associated with a gene, which is expressed in cotton fiber. Also provided is a novel cotton having a cotton fiber which has a natural color. The color was achieved by the introduction and expression in cotton fiber cell of a pigment gene construct.
EP0834566 provides a gene which controls the fiber formation mechanism in cotton plant and which can be used for industrially useful improvement.
However, beside Sucrose Synthase, there is no evidence to date that the expression of any particular gene plays an essential role in cotton fiber formation or enhanced fiber characteristics.
Thus, there remains a need for identifying other genes associated with fiber characteristics of cotton plants and a more thorough search for quality-related genes is required.
While reducing the present invention to practice the present inventors devised and employed a novel computational approach that utilizes comparative genomics to identify genes which play a pivotal role in fiber development. As demonstrated herein, expression of such genes correlates with fiber length and their overexpression is sufficient to modify tomato seed hair, an ultimate model for cotton fibers. These results suggest that polynucleotides of the present invention can be used for generating transgenic cotton plants which are characterized by fibers of desired length.